1. Field of the Invention
The present invention relates to an improved fixed dummy block assembly to be used with a heavy duty metal extrusion assembly so as to replace a standard dummy block with an assembly that is quick and easy to install and secure in place, as well as to remove and replace when necessary, and which significantly minimizes operation down-time generally associated with the preheating and parts replacement requirements of known dummy block assemblies, in a durable effective and adaptable assembly.
2. Description of the Related Art
A variety of large metal parts that are utilized throughout industry are made by heavy duty extrusion procedures. Simply put, the extrusion procedures utilize a quantity of heated, and therefore deformable, metal, in a large block generally called a billet. This metal billet is introduced into an extrusion assembly which pushes the billet through a specific die that defines the desired output shape. Often, however, because of the natural properties of the metal being utilized for extrusion, it is difficult to maintain a balanced billet consistency, which is neither too soft nor too hard, and is therefore appropriate for effective extrusion. Specifically, it is evident, that in order to enable the billet to be extrudeable in a typical extrusion procedure, it is necessary to maintain substantially high temperatures during operation so that the metal billet is softened and can be pushed through the die. Still, however, the operating temperatures must not be so high so as to make the metal billet soften to the point where it looses all its rigidity and is therefore unmoldable as it will not retain its extruded form when pushed through the die. As such, an ideal billet consistency will require that a substantial amount of force is exerted on the billet in order to push it through the relatively small openings of the die. Accordingly, a major cause for downtime and/or operational malfunctions during extrusion procedures relates to the substantial amounts of stress exerted on the extrusion equipment, and the substantially high operating temperatures which can weaken the structure of the extrusion equipment, thereby leading to breakage.
Conventional heavy duty metal extrusion assemblies generally include a hydraulic press and a billet container. In particular, the billet container includes a die end over which the extrusion die is positioned and from which the formed part exits. Accordingly, an interior wall surface of the billet container is structured to contain the metal billet as it is pushed towards the die in order to form the extruded part. Generally, the metal billet is pushed into the billet container, and towards the extrusion die, by an elongate stem connected to the hydraulic press. Disposed on an end of the stem is a dummy block which is structured to substantially ensure that metal from the metal billet only exits the billet container through the die. Further, conventional dummy blocks are generally sized to be substantially equivalent to an interior dimension of the billet container, thereby protecting, to the greatest extent possible, the stem and other operating parts of the extrusion press from being covered and possibly damaged by metal from the metal billet, and maximizing the overall percentage of the metal billet that is actually pushed through the extrusion die to form the finished part. Still, however, because some clearance must be provided if the dummy block is to slide into the billet container, and because of the heavy compression forces utilized during the extrusion process, some seepage of metal usually results over the surface of a conventional dummy block. While this seepage may not be sufficient to contaminate the stem or other portions of the extrusion assembly, the dummy block itself tends to become contaminated or otherwise coated to the point where it is inoperable and necessitates frequent replacement after a small number of uses. Furthermore, standard dummy blocks are generally aligned at a pin on the end of the stem. Subsequent to extrusion, however, such a pin interconnection is insufficient to pull back the dummy block and fully separate it from the remaining billet. As a result, a layer of metal often becomes stuck on the dummy block, requiring manual removal, often by chipping away with a hammer and/or chisel. Of course, such manual removal requires the cycling of multiple dummy blocks to avoid excess down time, and can easily lead to damage to the surface of the conventional dummy block. Accordingly, and because of the great expense and time delay associated with continuous standard dummy block replacement and/or cycling, others in the art have sought to implement alternative dummy block assemblies. These alternative dummy block assemblies are conventionally known as fixed dummy block assemblies. Specifically, fixed dummy block assemblies are structured to permit continuous or at least repeated use, and generally include a bell portion that is movably retained within the dummy block housing. In use, the bell portion of the fixed dummy block engages the metal billet first and is pushed back into the dummy block housing. Due to the great compressive force which is exerted on the billet by the bell and the resistive force provided by the billet as it resists compression and extrusion, the bell portion will engage the walls of the dummy block housing resulting in a flexing of the surrounding wall until the housing's exterior expands to within very small clearance of the interior surface of the billet container. Accordingly, as the fixed dummy block is inserted into the billet container, the perimeter diameter of the dummy block housing is slightly smaller than the interior surface of the billet container; however, when contact with the metal billet is made and the dummy block housing flexes outwardly, the perimeter diameter of the dummy block housing will be substantially equivalent to the interior surface diameter of the billet container such that very little space will remain between the housing and the sidewalls of the billet container to prevent significant outward seepage of the metal billet over the surface of the dummy block housing and therefore the stem. Conversely, when the fixed dummy block is removed from the billet container, the diameter of the fixed dummy block housing returns to its normal diameter and facilitated removal is achieved. This seepage prevention, which maximizes the amount of the metal billet that is used and protects the operating equipment, is therefore one primary reason why the use of a fixed dummy block assembly is substantially beneficial and cost saving for industries using heavy duty metal extrusion systems. Furthermore, the secure engagement between the fixed dummy block and the stem permits separation of the dummy block from the billet without the need to cut or scrape the remaining billet metal.
Still, however, there are a number of problems associated with fixed dummy block assemblies. One such problem involves the overall size of conventional fixed dummy blocks, and hence the manner in which the fixed dummy block portion of the assembly must be secured to an end of the stem. Conventionally, most fixed dummy blocks are necessarily quite long and heavy, as compared with standard dummy blocks, due to the intricate interior configurations necessitated by prior art dummy block assemblies. In particular, most prior fixed dummy blocks incorporate interior threaded and/or biased interconnections which call for added interior spacing for both operational and repair purposes. As such, prior art assemblies require a portion of the conventional sized stem to be cut off to a length which matches the precise length required by the fixed dummy block assembly to ensure maximum extrusion. Not only does this require extensive and possibly damaging cutting of the stem, but more importantly, such shortening of the stem makes the modified stem, and hence the extrusion assembly, substantially unusable unless an entire, matching, replacement fixed dummy block assembly is available.
Further, most conventional dummy block assemblies provide for securing of the fixed dummy block portion via a threaded connection. Such a design can be seen in U.S. Pat. No. 5,311,761 to Robbins. This design, as with many conventional fixed dummy block designs, includes a stud portion that is threaded into the cut off stem. If, however, the device breaks or becomes coated with excess metal and must therefore be replaced, the substantially high temperatures and the problems associated with the removal of partially broken threads make it quite difficult to remove the stud, and hence the fixed dummy block portion from the stem. For this reason, a device such as that in U.S. Pat. No. 5,272,900, also to Robbins, is provided to include a bayonet type connection between the stud and the stem. Unfortunately, however, while this improvement does generally facilitate removal of the fixed dummy block from the stem, it does not address a number of additional problems associated with fixed dummy block use.
In particular, after extensive experimentation it has been determined that the incorporation of a number of threaded elements and various separate components within the fixed dummy block itself can lead to significant disadvantages during use of the fixed dummy block assembly. Specifically, it is often the bell portion of the fixed dummy block which becomes contaminated or otherwise damaged while the remainder of the fixed dummy block assembly remains fully operational. As a result, efficiency considerations dictate that in certain circumstances the bell portion alone be removed and replaced, thereby saving the expense associated with the replacement of an entire fixed dummy block and minimizing the downtime required for obtaining and replacing the entire dummy block. Because of the expense of the overall dummy block portion of the assembly, many facilities only keep one fixed dummy block portion on hand. Unfortunately, even if the operators wish to replace only the bell portion, most fixed dummy block assemblies, even those which include a bayonet type stem connection as in U.S. Pat. No. 5,272,900, include a bell portion that is threadedly secured in place within the housing of the fixed dummy block by way of a bolt or like fastener element. Additionally, the bell portion may be connected to a variety of springs and the like within the housing of the fixed dummy block. As a result, under the substantially high temperatures associated with fixed dummy block use, it can be significantly difficult to remove the bell portion from its secured position within the fixed dummy block, especially if the bell, and/or some of its threaded connections are partially broken. Also, the conventional configuration and interconnection of the bell portion and the housing will generally necessitate that the access to the bell portion must be achieved from an interior of the fixed dummy block housing because only minimal portions of the bell are exposed from the housing and a substantial grip of the bell is necessary if it is to be effectively unscrewed. There is, therefore, a need for an improved fixed dummy block assembly which provides for convenient and facilitated removal of merely the bell portion of the fixed dummy block as well as facilitated removal of the entire fixed dummy block from the stem in a quick and effective manner. Furthermore, because the stud is screwed into the housing portion, even with a bayonet type stud-stem connection, appropriate disengagement of the stud from the stem cannot be achieved if the threaded stud-housing connection is broken and the stud cannot be rotated effectively by turning the stem. In this regard the removable stud must be employed to permit access to the bell-housing connection within the housing.
Further, during replacement of fixed dummy blocks, a major source of added cost and/or downtime generally relates to the requirement that the fixed dummy block be heated when mounted on the stem. The pre-heating is primarily done to minimize the risks of breakage or fracture of the fixed dummy block portion when introduced into the hot, high pressure operating environment. In particular, the preheating is especially directed towards heating the numerous threaded portions that are contained within the fixed dummy block assembly. Specifically, the commonly employed threaded interconnections between the entire fixed dummy block portion and the stem, between a stud and the fixed dummy block housing, and/or between the bell portion and the housing of the fixed dummy block are much more susceptible to shatter and breakage if exposed to substantial quantities of stress without being preheated. Unfortunately, however, because of the ridged, mating interconnection of the threaded portions, often within an interior of the fixed dummy block housing, the threaded connections are very difficult to fully heat and thereby necessitate direct preheating of the entire fixed dummy block portion in a special oven or heating unit. Also, if the threaded portion is the portion of the fixed dummy block assembly that shatters, it substantially increases the difficulty associated with removal and/or separation of portions of the fixed dummy block. Furthermore, because conventional fixed dummy blocks must be generally large and elongate due to their intricate interior mechanism, direct heating on the stem would take a substantial amount of time, a consequence that further leads to costly down time.
In addition to ensuring that the threaded portions within the fixed dummy block assembly are sufficiently preheated, another problem associated with conventional fixed dummy block assemblies involves ensuring that the threaded portions within the fixed dummy block are not overly hot. Specifically, the threaded portions of the fixed dummy block assembly are most susceptible to breakage because under the high temperatures and high stress, they are subject to some play or stretching during the constant load cycles endured by the fixed dummy block. Not only does this stretching of the threads lead to quicker breakage, but also the play between the threads increases as the gaps stretch even further such that the fixed dummy block assembly does not remain properly aligned as it is introduced into the billet container for compression of the billet. This improper alignment can lead to malfunctions in the extrusion cycle and can lead to excessive damage or wear to the billet container. It is therefore evident that there is a substantial need in the art to provide an improved fixed dummy block assembly which identifies the previously unaddressed and unidentified problems associated with the use of threaded portions within a fixed dummy block assembly by eliminating all threaded portions of interconnection within a simple and effective device. Additionally, there is a need in the art for an effective fixed dummy block assembly which is efficiently configured to be substantially compact thereby eliminating the need to cut the conventional stem of an extrusion press and allowing for rapid and effective heating of the fixed dummy block directly on the stem. Further, there is a need in the art for a fixed dummy block assembly which is capable of operating at the high temperatures associated with metal extrusion, but which is also capable of balancing temperatures therein to ensure that the fixed dummy block assembly itself does not get too hot so as to be subjected to excessive wear or potential deformation.